Method for producing dehaired hides with the aid of mold tryptases in alkaline solution



Patented Dec. 6, 1938 I METHOD FOR ra'onucmc DEHAIRED nmas WITH THE AID F MOLD myr- TASES IN ALKALINE sow-non Otto Riihm, Darmstadt, Germany No Drawing. Application October 5, 1936, Serial N0. 104,147. In Germany October 19, 1935 3 Claims. (Cl. 195-6) The invention relates to improvements in preparing hides for tanning and to the reagents employed in such preparation.

The present application is a continuation-im- 5 part of my prior application Serial No. 70,890 filed March 25, 1936 and the entire disclosure of said prior application is hereby incorporated by reference as part of the disclosure of the present application.

In my application Serial No. 70,890 there is described a method for depilating and bating skins and hides with the aid of mold tryptases, particularly those obtained from aspergillus varieties and using neutral to weakly acid solutions with the addition of sodium bisulphite. The action of this solution, according to said application, may furthermore be improved by the addition of ammonium salts. Prior to the mold tryptase treatment the skins and hides must be swelled by alkaline treatment.

The surprising fact has been ascertained that a good result may be obtained, including particularly a greater decrease in damage to the hide,

if the mold tryptase is caused to act in alkaline solution. The procedure may be such that the hides are pretreated as in my prior application,

with a solution of caustic soda and sodium sulphate and thereupon immediately treated in a depilatory bath with mold tryptase and addition of ammonium salts such as ammonium sulphate,

ammonium carbonate, etc. with so much sodium bisulphite added that the solution thus rendered alkaline by the alkali pretreatment still reacts alkaline after the addition of sodium bisulphite.

However, other reducing agents may also be used,

of the type of sodium sulphite or sodium thiosulphate, if desired, together with alkaline reacting salts such as sodium bicarbonate or soda.

A further improvement has been made in the process in that when depilating according to the method recited in the preceding paragraph, a

weaker alkali pre-swelling treatment suiiic'es than is indicated as necessary in my prior application.

To this end it is essential that the mold tryptase be made to act on the hide with a relatively small amount of water. The alkali swelled hides may be kneaded in a vat for one hour with the requisite amount of mold tryptase and the necessary addition agents while using 60 liters of water for each 100 kgs. weight of soft hide, or the alkali Finally it has been found that when depilating with mold tryptase in alkaline solution in a similar manner, it is possible entirely to avoid the alkaline swelling step previous to and during the mold tryptase treatment. The procedure is ef- 5 fected with mold tryptase and sodium sulphite in such alkaline or ammoniacal reaction that no swelling occurs. The alkaline or ammoniacal treatment may also be separate from the treatment with mold tryptase inasmuch as it may pre- 10 cede or follow the same. A preferred method is one wherein the hides or skins are coated with a solution of mold tryptase, sodium sulphite and ammonium sulphate and after being stored for one day and subsequently treated with a .5-1.5% 15,

soda solution, are then depilated.

It has also been found that the addition of ammonium salts or ammonia is suitable for preventing the occurrence of decay phenomena during the subsequent treatment with soda solution. By

avoiding the alkaline swelling, the hide substance, 20

hair and wool, are particularly saved from damage.

- Examples 1. 100 kgs. of calf hides, softened as usual, are 2 pretreated for two days with a solution of:

Caustic soda kgs 1.2 Sodium sulpha kg .8 Water liters 500 Thereupon the hides are placed in a liquor composed of: y

Mold tryptase F k 1 Sodium bisulphife 1 1 ka- 1 Water s" 35 and are kneaded for one hour in a vat. Next morning they may be depilated free from basic hair. The dehaired hides are then worked up further without subsequent bating.

2. kgs. of lamb skins, softened as usual, are 40 pretreated as in Example 1 with caustic soda and sodium sulphate and then coated on the fleshy After one day the hides may be depilated free from basic hair. I

3. 100 kgs. of lamb skins, softened as usual, are pretreated as in Example 1 with caustic soda and sodium sulphate and then coated on the fles y side as in Example 2, whereby however in lieu of .5 55

and allowed to lie for 24 hours.

kg. sodium sulphite, .8 kg. of sodium thiosulphate are used. The further treatment proceeds as in Example 2.

4. 100 kgs. of goat hides, softened as usual, are coated on the fleshy side with:

Mold tryptase kg 1.0 Sodium sulphite "kg..- .5 Ammonium carbonate kg .5 Water a1iters.... 6

After being allowed to lie for 24 hours the hides arelmmersed for 1-2 days in a solution of Water liters 40o Calcined soda kgs 5 After depilating, the dehaired hides are worked ,up as usual, that is, are defieshed, washed out,

After depilating, they are treated for several days with:

Water liters 400 Calcined soda kgs 5 or else are tanned without subsequent treatment, after being cleaned.

6. 100 kgs. sheep skins, softened as usual, are

immersed for two days in a solution of Water "liters" 400 Calcined soda kgs 5 After being allowed to drip, the hides are coated with a solution of:

Mold tryptase kg 1 Sodium sulphite kg 1 After being allowed to lie for 24hours the hides are freed from wool and worked up asusual, i. (2.

defleshed, washed out, smoothed, rinsed, and tanned.

7. Lamb skins normally limed with lime-arsenic are (after removal of wool) washed about 2 hours with soft water and then each 100 kgs. of dehaired hide is bated with:

Water at" a temp. of 25-30fC liters 300 Sodium bisulphite-; kg 1 Ammonium sulphate kg 1 Mold tryptase kg .35

The bating procedure may be prolonged over night. The next morning the dehaired hides are worked up as usual, i. e. defleshed, smoothed, rinsed and finished.

, I claim:-

1. In the preliminary treatment of hides preparatory to tanning wherein the hides are first swelled by alkaline treatment and subsequently treated with a mold tryptase in a neutral to weakly acid solution with the addition of a reducing agent selected from a group consisting of sodium bisulphite, sodium sulphiteand sodium thios-ulphate; the improvement which comprises adding only so much of the reducing agent to the enzyme that the alkaline solution produced by the alkali pre-swelling reacts alkaline even after the addition of the reducing agent.

2. In the preliminary treatment of hides preparatory to tanning wherein the hides are first swelled by alkaline treatment and subsequently treated w th a mold tryptase in a neutral to weakly acid solution with the addition of sodium bisulphite; the improvement which comprises adding only so much of the sodium bisulphite to the enzyme that the alkaline solution produced by the alkali pre-swelling reacts alkaline even after the addition of the sodium bisulphite.

3. A process as set forth in claim 2, wherein at least one weak alkali selected from a group consisting of sodium carbonate, sodium bicarbonate and ammonium salts is used with the sodium bisulphite.

o'rro RoHM. 

